2018/01/03 by Priyadarshini Thiyam, Prachi Parashar, K. V. Shajesh +5 · 1 citation
Physics and Astronomy · #cond-mat.mes-hall #hep-th #quant-ph
paper · pdf · doi:10.1103/physrevlett.120.131601
published as Phys. Rev. Lett. 120, 131601 (2018) · 6 pages, 5 figures, accompanied by a supplementary material
arxiv created 2018/01/03 · arxiv updated 2018/04/04
The Casimir-Lifshitz torque between two biaxially polarizable anisotropic planar slabs is shown to exhibit a non-trivial sign-reversal in its rotational sense. The critical distance ac between the slabs that marks this reversal is characterized by the frequency ωc ∼ c/2ac at which the in-planar polarizabilities along the two principal axes are equal. The two materials seek to align their principal axes of polarizabilities in one direction below ac, while above ac their axes try to align rotated perpendicular relative to their previous minimum energy orientation. The sign-reversal disappears in the nonretarded limit. Our perturbative result, derived for the case when the differences in the relative polarizabilities are small, matches excellently with the exact theory for uniaxial materials. We illustrate our results for black phosphorus and phosphorene.